// Copyright 2022 Criticality Score Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package algorithm

import (
	"math"
)

type Distribution struct {
	normalizeFn func(float64) float64
	name        string
}

func (d *Distribution) String() string {
	return d.name
}

func (d *Distribution) Normalize(v float64) float64 {
	return d.normalizeFn(v)
}

var (
	normalizationFuncs = map[string]func(float64) float64{
		"linear":  func(v float64) float64 { return v },
		"zipfian": func(v float64) float64 { return math.Log(1 + v) },
	}
	DefaultDistributionName = "linear"
)

func LookupDistribution(name string) *Distribution {
	fn, ok := normalizationFuncs[name]
	if !ok {
		return nil
	}
	return &Distribution{
		name:        name,
		normalizeFn: fn,
	}
}
